The invention relates to a method and apparatus for controlling the casting of molded products and in particular to the control of automatic casting machines having a tilting casting ladle.
In automatic casting equipment, repeated difficulties occur in determining the amount of castable material such as molten metal or the like, required in order to provide a charge capable of completely and satisfactorily filling the mould. Different proposals have become known in order to eliminate these difficulties.
The simplest way of determining the amount has been by measuring the time during which the molten castable material is poured. This system fails, because the amount of material per unit time flowing out of the ladle is highly dependent on the height of the "bath level" (i.e. upper surface) of the molten material above the discharge gate of the ladle nozzle or spout. Rapid, intermittent tilting motions, which cannot be avoided with manual control, cause periodic fluctuations of the bath level. These fluctuations of the bath level lead to inaccuracies in metering the volume poured in any given time period. The temperature and the chemical and physical composition of the material also have influence on the amount of material flowing out of the ladle, per unit time. In addition, the opening of the nozzle spout or valve which is preferably formed of crystalline graphite becomes slightly larger in the course of even a single operating cycle.
In general, the three influences, aforementioned, can be easily compensated for, by correcting the time adjustment during which pouring takes place, since the casting temperature and the analysis of the material are, for technological reasons, subjected to rigorous pre-monitoring and therefore fluctuate during casting only within very narrow limits, and the change of the opening of the nozzle takes place very slowly. Any time correction which is necessary on account of this last influence, is only required at only larger, regular time intervals. On the other hand compensation for fluctuations caused by tilting errors, manual operation etc. cannot be so easily compensated for.
It is an object of the present invention to provide a method by which it is possible, in a simple and reliable manner, to determine the material quantity for every casting operation even in repeated cycles, with satisfactory accuracy without excessive material being lost and while insuring a complete filling of the moulds.